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The Australian coast can be subdivided into three broad sedimentary provinces occupying the east, south, west, and northwest coasts. The 11,978-km long eastern province extends from the western Gulf of Carpentaria along the entire east coast to eastern Tasmania. It is characterized by tropical to temperate humid climates, quartz sediments, and overall northerly sediment transport, with significant onshore transport where shoreline orientation and wave and wind energy combine to produce massive coastal dune systems, including the world's largest sand islands. The 9587-km long south and west coast province has an arid to semiarid climate with little terrigenous sediment. Much of the coast faces into the prevailing southerly winds and the high year-round Southern Ocean swell, resulting in massive transfer of shelf and nearshore carbonate-rich sediments to the shore and into extensive coastal barrier-dunes systems, the largest dunes extending 110 km inland. The 9106-km long northwest province has a tropical arid to monsoonal climate with coral reefs fringing parts of the coast and has predominately offshore winds. While several large rivers deliver substantial terrigenous sediment to the coast, little is deposited above sea level.
On many tidal flats, there is a transition from sand flat at the more energetic seaward margin to mudflat further inland. However, the ability of sand flats to attenuate incident wave energy is an important but poorly understood constraint on mudflat development and morphology. This paper presents the results of an instrumented field study of incident wave attenuation across Roberts Bank, the sandy intertidal portion of the Fraser River Delta. The attenuation of wave height was monitored at four stations along a shore-normal transect for a period of 2 months (December 23, 2003, to February 10, 2004). The attenuation varied with the relative wave height ratio (Hs h−1) along the seaward margin, with dissipation increasing as water depths decrease and/or incident wave heights increase. Under the most dissipative conditions observed (Hs h−1 ≈ 0.25), the exponential decay coefficient reached 0.00045. This decay coefficient is an order of magnitude smaller than predicted by a simple wave transformation model due to the relatively large wind fetch over the sand flat. Despite the maintenance of wave energy, the range of wave heights remains constrained in the landward direction, with the frequency of waves capable of entraining sediment on the sand flat decreasing from 11% at the outer flat to 2% at the inner stations. In response, bed elevation change and depth of sediment activation are greatest at the seaward margin and decrease exponentially landward. It is argued that the sand flat provides a natural barrier that defines the extent of mudflat development by limiting the potential for sediment resuspension and morphological change on the mudflat.
This work presents empirical data from several databases. Empirical data ultimately form the basis for most ecological/environmental studies, and this work uses what may be the most comprehensive data set ever compiled concerning relationships between chlorophyll-a concentrations, nitrogen, phosphorus, and salinity, since the data in this study concerns about 500 lakes and coastal areas. The focus has been on how variations between systems in median summer values of chlorophyll-a concentrations (Chl) depend on variations in total nitrogen, total phosphorus, and salinity. The salinities range from 0 to 275 PSS78 in hypersaline systems; the median salinity is 12.5. The range in nutrients is from ultraoligotrophic (totalP, or TP, is less than 1 μg/L) to hypertrophic systems (TP is greater than 1000 μg/L). The chlorophyll values vary from 0.12 to 60 μg/L. Results showed that there is a minimum in the Chl/TP ratio in the salinity range between 2 and 5, followed by an increase up to a salinity range of 10–15, and then a continuous reduction in the Chl/TP ratio until a minimum value of about 0.012 is reached in hypersaline systems. We have also identified a threshold value for the salinity. In systems dominated by freshwater influences, the ratio of Chl to total nitrogen, or TN, increases steadily from about 0.008 in lakes to 0.02 when the salinity is 10. At higher salinities than 10, the Chl/TN ratio decreases in a nonlinear fashion. We have also presented several empirical models to predict chlorophyll concentrations from levels of TP, TN, and salinity. The model predicting Chl from TP and salinity is generally the best one. The next best model according to the criteria (r2 value, median error, and standard deviation for the error) is the model using TN and salinity. Models not including salinity predict chlorophyll less well.
Coastal areas are facing serious threats from both manmade and natural disturbances; coastal erosion, sea-level variation, and cyclones are the major factors that alter the coastal topography and coastal resources of the island ecosystems. The impact of natural disturbances can be reduced by protecting the coast by green shielding. The present study was carried out to understand the coastal geomorphology and coastal resources of Rameswaram Island, India, using Indian Remote Sensing Satellite (IRS)-P6 Linear Imaging Self-Scanning (LISS)-III sensor imagery (2005) and to find suitable areas for bioshielding of this island using mangroves and casuarinas. The study found satellite imageries, along with field survey, will be useful tools for delineating the coastal geomorphology and coastal resources and finding suitable areas for bioshielding.
Coastal morphometry has importance for water exchange and affects primary production potential, in that the bathymetric shape of a coastal area determines how much of the bottom area is reached by sunlight and hence is available for benthic primary production. In this paper, morphometric production potential, here defined as the bottom area above the Secchi depth, was assessed with the use of geographical information systems, morphometric data, and Secchi depth data, exemplified with data from the whole Swedish coast. The spatial distribution of ecologically important areas with high morphometric production potential was quite even along the Swedish coastline, but some regional differences were found. A linear relationship was found between the Secchi depth and the bottom area above the Secchi depth for the Swedish coast. An equation for calculation of the bottom area below/above a certain depth in lakes was used to calculate the area above the Secchi depth for 541 coastal areas, and the results were compared with the corresponding area values extracted from hypsographic data. This test yielded good correlation (r2 = 0.87), and the equation was found to be useful also in coastal areas (e.g., when detailed hypsographs are not available).
This article describes the transport processes and net salt flux within a shallow estuarine system, with particular reference to the Coombabah Lake–Creek system in Queensland, Australia. Observations of currents and salinity at two locations within Coombabah Lake provided a basis for assessing the relative importance of various transport processes within a very shallow (water depth <1 m) subtropical estuary. The instantaneous velocity and salinity data were decomposed into time-averaged means and time-varying components and were used to quantify the salt flux components attributed to various physical processes. In this study, advection by residual flow, which contributed 65% of the total salt flux, was identified as the dominant process in transporting salt. The advective flux also determined the direction of the net salt flux within this shallow estuarine system. This study concludes that the net salt flux varies spatially and temporarily with hydromorphological and meteorological conditions.
Porous breakwaters using a caisson-pile group can increase the resistance of the vertical coastal structures in harbors to external heavy impacts, and also help facilitate the exchange of water. This article presents experimental results for the hydraulic performance of independent caisson-pile type breakwaters having three rows of vertical piles, both evenly and unevenly spaced between rows. Compared with even spacing, uneven, sparser spacing tends to have lower wave reflections and higher energy loss coefficients. Wave transmission, by contrast, appears not to be considerably influenced by spacing pattern. The transmission coefficient increases with wave steepness (S0,s) and decreases with the ratio of the (total) width of the three pile rows to the wavelength (W/L0,s).
An assessment of variation in beach volumes is needed to better understand beach behaviour and to monitor changes in an attempt to manage beach volume distribution through targeted intervention. Mixed sand and gravel beaches, as well as gravel beaches, are distinct from sandy beaches in that they often have multiple steep (>20° or 1 : 4) berms on the upper part of the beach and short-wavelength (<20 m) longshore variations in the form of beach cusps or in close proximity to groynes. This paper discusses a range of ground survey and remote sensing methods for surveying mixed beaches, methods of point collection in relation to the different methods, and subsequent interpolation to calculate beach volumes. Particular emphasis is given to high-density surveys by Global Positioning System (GPS) with a rover attached to a wheel. Results show that average surface elevation changes greater than ±0.04 m can be reliably detected and that the method, if carried out using cross-shore profiles, provides a useful tool for beach monitoring in scientific projects interested in inferring processes from the surveys and that have a temporal resolution from tides to weeks. For surveys predominantly interested in monitoring total beach volume, GPS surveys with a quad bike (all-terrain vehicle) might be more economical while providing only marginally poorer results if surveys coincide with minimum cross-shore variation during spring tide. Comparisons between ground surveys with GPS and remote sensing methods like LIDAR or airborne photogrammetry are also discussed.
The context underlying the concept of Process-Defined Management Units (PDMUs) as an aid to sustainable coastal decision-making is reviewed. Using examples, it is suggested that the flexible PDMU approach can help to pragmatically integrate coastal management and has considerable merits compared with other types of coastal management units, such as sediment cells and Homogeneous Environmental Management Units (HEMUs).
Santa Rosa Island, situated along the northwestern Florida coast facing the Gulf of Mexico, is an 85-km-long wave-dominated low-lying barrier island with well-developed incipient and established dunes. In this paper, we examine the regional-scale effect on coastal dunes by a strong category 3 hurricane, Ivan, through comparison of pre- and poststorm airborne LIDAR (light detecting and ranging) surveys. On the basis of pre-Ivan LIDAR survey data, the elevation of the berm and back beach is typically 2.0 m above MSL (mean sea level). Incipient dunes range from 2.5 to 10 m above MSL, or 0.5 to 8.0 m above the surrounding beach. The hummocky dunes that developed over relic washover platforms are typically less than 4.0 m above MSL. The densely vegetated, established dune fields are composed of dunes less than 7.0 m high and intradune wetlands lying at less than 1.0 m above MSL. The entire island was severely affected by Ivan, which made landfall about 45 km to the west in September 2004. The landscape was substantially changed by Ivan. Over 70% of the incipient and hummocky dunes were destroyed, and a large portion of the low-lying wetlands was covered by washover. The degree of storm-induced morphology change depends not only on the intensity and duration of the storm but also on the antecedent morphological characteristics of the barrier island. Comparison of pre- and post-Ivan cross-island LIDAR profiles indicates that at most locations, more sand was eroded from the subaerial portion of the barrier island (e.g., beach and dune) than was deposited as washover terraces and lobes. This suggests a net sand loss to the offshore region. Evidence of sand moving alongshore related to the oblique orientation of the dunes was also identified. Under inundation regime, the subaerial sediment deficit could be accounted for by subaqueous sedimentation into the back-barrier bay.
Numerical modeling of dredged pits is conducted to investigate the hydrodynamic and morphodynamic interaction in offshore sand extractions. Based on an analytical formulation, a semianalytical numerical model (MEMPITS) has been developed to study the morphodynamic evolution of offshore (ho > 20 m) sand borrow areas. The numerical model has been applied to study the morphodynamic evolution of two offshore sand borrow areas in the Balearic Islands (Spain). Field data allowed a detailed characterization of the evolution of the sandpits. Time series of local hydrodynamics have been obtained using generation models (hindcast) combined with local wave and flow models. A verification of the simple model has been carried out using relatively slight adjustments to the calibration factors. The simple model provides good estimates of the infill rate and migration velocities of the offshore pits on the scale of years. This semianalytical tool allows a quick systematic investigation of the physical mechanisms as well as a detailed sensibility analysis regarding the pit design parameters. These parameters include location (water depth), pit length, width, depth, and orientation with respect to the mean flow. A nondimensional analysis based on the model is also carried out to explore the role of the different variables involved in the evolution of offshore sandpits. Based on the field data and the nondimensional analysis, some basic design recommendations for offshore sandpits are proposed.
Sediment budget analyses conducted for annual to decadal timescales report variable magnitudes of littoral transport along the south shore of Long Island, New York. It is well documented that the primary transport component is directed alongshore from east to west, but relatively little information has been reported concerning the directions or magnitudes of cross-shore components. Our review of budget calculations for the Fire Island coastal compartment (between Moriches and Fire Island Inlets) indicates an average deficit of 217,700 m3/y. Updrift shoreline erosion, redistribution of nourishment fills, and reworking of inner-shelf deposits have been proposed as the potential sources of additional sediment needed to rectify budget residuals. Each of these sources is probably relevant over various spatial and temporal scales, but previous studies of sediment texture and provenance, inner-shelf geologic mapping, and beach profile comparison indicate that reworking of inner-shelf deposits is the source most likely to resolve budget discrepancies over the broadest scales. This suggests that an onshore component of sediment transport is likely more important along Fire Island than previously thought. Our discussion focuses on relations between geomorphology, inner-shelf geologic framework, and historic shoreline change along Fire Island and the potential pathways by which reworked, inner-shelf sediments are likely transported toward the shoreline.
Coastal areas of Orissa State in the northeastern part of the Indian peninsula are potentially vulnerable to accelerated erosion hazard. Along the 480-km coastline, most of the coastal areas, including tourist resorts, hotels, fishing villages, and towns, are already threatened by recurring storm flood events and severe coastal erosion. The coastal habitats, namely the largest rookeries in the world for olive Ridley sea turtles (the extensive sandy beaches of Gahirmatha and Rushikulya), Asia's largest brackish water lagoon (the “Chilika”), extensive mangrove cover of Bhitarkanika (the wildlife sanctuary), the estuarine systems, and deltaic plains are no exception. .The present study therefore is an attempt to develop a coastal vulnerability index (CVI) for the maritime state of Orissa using eight relative risk variables. Most of these parameters are dynamic in nature and require a large amount of data from different sources. In some cases, the base data is from remote sensing satellites; for others it is either from long-term in situ measurements or from numerical models. Zones of vulnerability to coastal natural hazards of different magnitude (high, medium, and low) are identified and shown on a map. In earlier studies, tidal range was assumed to include both permanent and episodic inundation hazards. However, the mean of the long-term tidal records tends to dampen the effect of episodic inundation hazards such as tsunamis. For this reason, in the present study, tsunami run-up has been considered as an additional physical process parameter to calculate the CVI. Coastal regional elevation has also been considered as an additional important variable. This is the first such study that has been undertaken for a part of the Indian coastline. The map prepared for the Orissa coast under this study can be used by the state and district administration involved in the disaster mitigation and management plan.
Wavelet analysis is considered a state-of-the-art technique in signal processing; it transforms the signal into a scale-time representation (scalogram) with high resolution, preserving the temporal characteristics of the signal. In the present study, an overview of Fourier analysis, short-time Fourier analysis, and wavelet analysis are given, and the differences between them are addressed. To demonstrate the importance of wavelet analysis in the field of coastal engineering and other related fields, a summary of the recent literature concerning its applications is given first, and then wavelet analysis is used to analyze the complex phenomenon of wave growth due to a sudden change in the wind conditions. This study shows that the temporal characteristics of the time series of wind speed and significant wave height can be explored qualitatively by using the complex Morlet wavelet analysis. The results reveal that the waves are responding immediately to the sudden change in wind conditions.
To detect the spatial characteristics of coastal landforms in a section of the Nile Delta region (Egypt) between 1984 and 2006, multitemporal satellite imagery was examined. The study area between Gamasa drain and Kitchner drain (Northern Nile Delta) shows significant changes that are supposed to be functions of the aeolian and coastal processes. This is, however, not the case where unprecedented human activities played a trigger factor in reshaping this area. The intervention of human activities in this area has resulted in a significant transformation of the existing landforms and introduced new land use classes. Remote sensing techniques offered a real-time source of information that aided in determining 11 landforms or use classes. A geographic information system spatial analysis model has generated a spatial matrix that quantified the rate of changes and therefore defined the controlling factors of such a highly dynamic environment. The local economy and socioeconomic circumstances have been shown to be driving forces of landforms transformation in favor of developing reclaimed land and fish farms. These two land use class were significantly increased by 37% and 11% of the total area in the last two decades, respectively.
Here, for the first time, fluorescence microscopy (FM) was coupled with leaf autofluorescence to visualize and track trace levels of anthracene (An) in living Kandelia candel (L.) Druce leaves, without destructive chemical extraction techniques. The experimental results revealed that, after tracking over 96 hours, An adsorbed onto the leaf surface was moved through the upper cuticle and through the stomata of the lower side into the internal leaf tissues. An was identifiable in six separate locations within the K. candel leaves: the first hypodermis, the second hypodermis, and the upper palisade tissue moving from the upper cuticle; the lower hypodermis and the lower palisade tissue moving from the stomata of the lower side; and the spongy mesophyll moving from both sides. Under the same exposure conditions, the impact of An adsorbed at the center of the upper side of the leaf surface was much less than that at the edges of the leaf surface. However, after 96 hours of exposure to An, the amount of An transferred into the inner leaf tissues at the center of the leaf was higher than at the edges, which might provide important new information concerning how An enters, is moved, and is distributed within the K. candel leaves. Furthermore, this FM technique provided us with a noninvasive tool for visualizing and tracking the movement and storage locations of PAHs within K. candel leaves based only on the autofluorescence of leaf tissues as revealed by fluorescence microscopy.
The Mississippi Delta has long been characterized as an area of rapid subsidence; however, recent subsidence rates are substantially lower than previously reported. Tide-gauge records indicate that rates of relative sea-level rise were slow from 1947 until the mid-1960s, relatively fast from the mid-1960s until the early 1990s, and then slow since the early 1990s. These trends and rates are independently verified by repeat benchmark surveys and height monitoring at continuously operating geographic positioning system stations. Subsidence rates for the slow periods were a few millimeters per year, comparable to rates averaged over geological time scales that are attributed to natural processes such as shallow sediment compaction and deep crustal loading. The decadal pattern of slow, then rapid, then slow subsidence may be caused by natural deep-basin processes (e.g., gravity gliding and salt migration), but it is more likely related to rates of hydrocarbon production that followed the same temporal trends. If accelerated subsidence was primarily induced by reservoir compaction and fault reactivation associated with fluid withdrawal that also accelerated in the 1960s and 1970s, then the recent reductions in subsidence rates likely reflect a balancing of subsurface stresses and a return to near preproduction conditions.
Ecotourism in protected areas is growing rapidly all around the world. Although the benefits of ecotourism are well described, it is not a panacea for solving the complex human needs and resource-capacity paradox in protected areas, unless it is well planned and managed. The notion of ecotourism in legally protected areas is relatively new in Turkey, and therefore none of Turkey's 39 national parks has an ecotourism master plan. The purpose of this study is to analyze the ecotourism potential and to generate initial recommendations for establishing an ecotourism framework for Gallipoli Peninsula Historical National Park (GPHNP) in Çanakkale, Turkey. Three basic research steps are followed: analysis, evaluation, and synthesis. Natural, cultural, and historical features of GPHNP are presented, and a set of recommendations are provided with respect to ecotourism in the study area. Results indicate that the national park has substantial potential for ecotourism activities such as bird-watching, photo safari, wildlife watching, sportfishing, bicycling, scuba diving, farming tourism, flora tourism, trekking, and horseback riding through nature; and this potential is not sufficiently utilized in the current context. The recommendations include that the national park's war history, biological diversity, coastal morphology, and climate should be promoted holistically, and awareness of them should be raised. The topography and other landscape attributes of the park must be protected and sustained.
KEYWORDS: magnetic susceptibility, frequency-dependent susceptibility, magnetic minerals, Beach sediments, ferrimagnets, Maharashtra, West Coast, India
The beaches under study are characterized by distinctly different magnetic signatures in terms of their concentration and magnetic grain sizes. Seasonal variation in accumulation and erosion is seen at Vengurla Beach (Stations 1–7), which is moderate to very low premonsoon, high to low during monsoon season, and low to very low postmonsoon. Presence of fine single domain magnetic grains is moderate to high premonsoon, moderate to low during monsoon, and low postmonsoon at stations 1, 4, 7 (Vengurla beach), and 8 (Aravali beach). Aravali Beach has a very low concentration of magnetic minerals, precluding realistic assessment of its seasonal accretion–erosion pattern. At Redi Beach (Stations 15–20), the concentration levels of magnetic minerals are high premonsoon, which further increases during monsoon season, although at certain locations the rise continues postmonsoon. The sediments of these three beaches have variable proportions of magnetite, titanomagnetite, and hematite. The concentration of magnetic minerals is more at the northern (Stations 1 and 2) and southern (Stations 16–19) ends of Vengurla and Redi beaches, respectively. The provenance of magnetite and titanomagnetite can be attributed to Deccan traps and relict sands.
This technique can complement the conventional methods and underlines the utility of magnetic parameters in studying sediment movement along the beaches.
The coarse sediment fraction of geologic formations exposed in 42 km of southern California seacliffs in the Oceanside Littoral Cell was estimated using more than 400 samples. An impulse laser, oblique photographs, and coastal maps were used to define thickness and alongshore extent of the geologic units exposed in the seacliffs. The coarse sediment (defined as diameter > 0.06 mm) fraction in each geologic unit was estimated by sieving. About 80% of the exposed cliff face is coarse and can contribute to beach building. Finer cliff sediments are transported offshore by waves and currents. Although there are some differences, the observed 80% coarse fraction is generally consistent with previous estimates based on an order of magnitude fewer samples. Coastal development has largely eliminated about 40% of seacliffs in the Oceanside Littoral Cell as potential beach sand sources. For the remaining seacliffs, 1 cm of average cliff retreat yields 10,000 m3 of potential beach-building material.
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